Does Unity Ads not work in a Coroutine? [Solved]

I want to display unity ads after a short delay at the End screen of the game i'm working on. So i decided to do a simple coroutine as below

Code (CSharp):

1. StartCoroutine ("WaitOneSec");
2.  
3. IEnumerator WaitOneSec(){
4.         yield return new WaitForSeconds (1f);
5.         advertisement.SendMessage ("ShowVideoAd");
6.     }

If i were to use advertisement.SendMessage ("ShowVideoAd"); on its own the advertisement would show, but when i try it with the StartCoroutine it does not.

 

Nvm i'm an idiot. i have paused the game with Time.timeScale = 0 when the game ends. with the game paused the WaitForSeconds did not work.